Mercury Water Pressure Gauge Tubing Failure

[tomolalla]

I'm the second owner of a 2014 170 Montauk with a 2014 Mercury 90-HP FOURSTROKE engine. The boat came with a Mercury water pressure gauge. It appears to be a standard package from a local Boston Whaler dealer.

The engine water pressure gauge was not working, and I found the problem. The [tubing from the engine to the water pressure gauge] was broken in the rigging tunnel. A chunk of very brittle tubing was found in the bilge. It was as fragile as a piece of uncooked spaghetti.

The tubing was marked “SUN RISE POLYURETHANE.” I've read that polyurethane is susceptible to chemical breakdown.

I am wondering if [the 2014 170 MONTAUK boat’s engine water pressure gauge] was rigged using the wrong kind of tubing..

Q1: Is [a brittle tubing marked “SUN RISE POLYURETHANE”] the correct OEM tubing for the engine water pressure gauge?

Q2: what type tubing does Mercury use to connect the engine to their water pressure gauge?

Q3: is the water pressure gauge and tubing installed at the factory or at the Boston Whaler dealer selling the boat?

Most likely I will pay about $50 to buy some OEM tubing, and I will spend a couple hours running the tube from engine to console.

To know if someone put in the wrong tube or if the OEM tube falls apart in less than 10 years would be good.

[jimh]

By c.2014 the typical production 170 MONTAUK would be shipped from the factory to the dealer with the engine installed and fully rigged.

Based on some photographs of the helm console other 170 MONTAUK boats of that era, my inference is three standard engine gauges were provided with a 170 MONTAUK. From Port to Starboard across the top of the instrument panel, a 170 MONTAUK would have a 4-inch engine speed gauge (tachometer), a 2-inch Voltmeter, and a 2-inch water pressure gauge.

Q3: is the water pressure gauge and tubing installed at the factory or at the Boston Whaler dealer selling the boat?

On the basis I described above, my inference for your 2014 170 MONTAUK boat is the gauge and the plastic tubing were installed at the factory.

I suspect that the tubing for conveying the engine water pressure to the water pressure gauge is made to be semi-rigid so that there is a more accurate measurement of the actual engine pressure than if a softer material were used for the tubing.

The cause of the break in the tubing in the rigging tunnel may be due to a latent defect in the tubing or to damage done to the tubing during installation or to continual abrasion of the tubing from vibration and rubbing against some other object in the rigging tunnel during boating. Perhaps there was a kink placed in the tubing during installation, and this eventually led to a break in the tube. Or maybe the tubing had a splice that was concealed in the rigging tunnel.

This failure of a plastic tubing for an engine water pressure gauge seem rare.

I think you could replace the tubing in less than “a couple hours” of labor, using a similar tubing as was used originally.

I read that polyurethane is susceptible to chemical breakdown.

I doubt there is intrinsic risk of future repeat failure if a similar semi-rigid tubing material is used in the replacement. See if the tubing is sold separately by Mercury. I would expect that usually it comes as part of the water pressure gauge kit.

[jimh]

Further to the standard gauge package, see illustration 58-07 at

https://continuouswave.com/whaler/cetac ... age58.html

The caption states:

The factory standard gauge package includes a Tachometer, a battery voltmeter, and an engine cooling water pressure gauge.

[tomolalla]

Thanks for the information.

The tube was definitely deteriorated. Several six inch long chunks were found in the bilge that would easily break into smaller ones when I bent them. Other parts of the same tube, such as under the cowling and in the console look like new. So I'm not sure why the tunnel made a difference. Maybe that portion was occasionally immersed in water or chemicals used to clean the boat? It was definitely out of the sun so UV deterioration is not a concern.

Its good to hear that this is a rare occurrence so I will just purchase a Mercury OEM tube and see if it was the same kind. I know this should be a 30 minute job, but I have now become used to multiplying my repair estimate by 4Xs (find tools and parts, get rid of old tube, get coffee, hurt knees, swearing, find new problem and fix, get a beer, clean up).

[jimh]

In my first draft of my reply I had mentioned that perhaps a previous owner liked to wash down the deck with some hard detergent or other cleaners—like oxalic acid—and they puddled and settled in the rigging tunnel, where they were able to work on the plastic tubing. But I thought more about it, and decided that was a bit far-fetched, and I deleted those remarks. So maybe that conjecture was or is somewhat reasonable.

Yeah, every time I work on the boat the time involved is so much greater than I expected that I marvel at how much money I saved by doing it myself because I would never be able to afford to hire someone for that many hours to do the work.

To fish a new length of tubing through the rigging tunnel should not be too difficult. An electrician’s fish tape will be helpful. One you buy one you will be amazed how you ever lived without one. Remember, the guy with the most tools wins.

[GoldenDaze]

I had to replace the water pressure line from the engine to gauge in my 2003 160 Dauntless when it got brittle and started to leak. Of course, that boat is more than ten years older than yours, so I'm a little surprised yours was in such poor shape so quickly. I took a piece to a local auto parts store and got a length of vacuum tubing. Beware, there's a lot more tubing there than you might think! I figured "hey, it's only a 16-foot boat and the console's more-or-less in the middle, so 15 feet should be plenty." Naturally I ended up a foot short.

[jimh]

There is a derivative of Murphy’s Law in electrical work:

Any cable cut to length will be too short.